Efficient metoprolol degradation by heterogeneous copper ferrite/sulfite reaction

Metal/sulfite systems are currently used for SO •− 4 generation and oxidative removal of organic contaminants. However, homogeneous metal/sulfite systems are limited because their working pHs must be acidic and metal ions cannot be separated from the bulk reaction solution. As a consequence, these drawbacks have severely limited the application of metal/sulfite systems in real conditions. To address these issues, we tested the use of copper ferrite (CuFe 2 O 4 ), a ferromagnetic nanoparticle, to catalyze sulfite oxidation for the degradation of the metoprolol drug. The reaction mechanism was investigated by electron spin resonance, X-ray photoelectron spectroscopy, and radical quenching assay. The effects of pH, CuFe 2 O 4 , and sulfite dosages were also assessed. Results show that SO •− 4 was the primary radical responsible for metoprolol degradation. Higher pHs induced more metoprolol degradation using CuFe 2 O 4 /sulfite. Moreover, CuFe 2 O 4 remained morphologically intact and catalytically active after four batches of recycling. Overall, our findings show that CuFe 2 O 4 /sulfite can effectively degrade water contaminants in alkali pH and withhold catalyst activity after multiple reuses, therefore addressing the issues associated with homogeneous metal/sulfite systems.